130 PRACTICAL ORGANIC CHEMISTRY Reactions.—i. Add to the solution of alloxantin a little t>a.ryt;L water ; a violet colouration is produced. 2. Add ammonio-silver nitrate solution and warm ; rneta,lHc silver is deposited. 3. Boil the solution with mercuric oxide ; a violet solution of murexide is formed. PREPARATION 41. Alloxan (Mesoxalylurea), CONH;CO Liebig, Wohler, Annalcn, 1838, 26, 256. 5 grms. alloxantin. 5 „ (3*5 c.c.) cone, nitric acid (sp. gr. 1-4). 10 „ (7 c.c.) fuming „ (sp. gr. 1-5). The finely powdered alloxantin is added to a mixture of the strong and fuming nitric acid, and left to stand. Slight evolu- tion of nitrous fumes occurs, and the alloxantin, which at first remains at the bottom of the vessel, slowly changes into tin* more bulky crystals of alloxan, which gradually fill the licjuicl. The reaction lasts about two days, and is complete wlien a sample dissolves readily and completely in cold water. "I" IK? crystalline mass is spread upon a porous plate, thoroughly dried in the air, and freed from traces of nitric acid by heating in a basin on the water-bath, until the smell of the acid disappears. Alloxan may be obtained in large crystals by dissolving' tlie dry product in the smallest quantity of hot water, and allowing" the solution to evaporate slowly in a desiccator over sulphuric a.cicL The crystals are liable to effloresce. C8H4N407 -!- O - 2C,,H,N,04- Alloxantin. Alluxan. Properties.— Colourless crystals, containing 4 molecules oi water of crystallisation. . Reactions. — i. A small quantity of the alloxan solution is evaporated to dryness on the water-bath in a porcelain ~ba.sin. A reddish residue is left, which turns purple on the addition of ammonia (murexide). See Appendix, p. 268.